I don't think I'm going to go round there, although if they wanted to they could now just walk out into my back garden and look straight in to my flat!! I'll be keeping my doors firmly locked!
I had no idea it was a criminal offence! I'm seriously worried that they are going to come round to mine when they get in. The builders must have told them what happened?? If they are the type of people who are so blasé about a situation like this in the first place then I don't imagine they are going to be particularly pleasant to deal with.
And I'm in on my own tonight 
I now feel like I have to hide incase they see me, which I won't because it's bloody ridiculous and they are very clearly in the wrong, but still, horrible situation!!!
I am hoping they have seriously just made a mistake, are very apologetic, and put it back to how it was, however, I HIGHLY doubt it.